A horizontal reactor with internal oncoming flow bottoms with all the devices necessary for the operation of such a reactor has been known from DE 43 26 562 C2.
The horizontal fluidized bed reactor according to DE 43 26 562 C2 has a drawback, namely, that it can operate only with a predetermined particle size spectrum, which is determined by the oncoming flow velocity (fluidization velocity) in the fluidized bed. Thus, a different particle size spectrum requires different oncoming flow velocities. In addition, screen classification is necessary before charging the material onto the fluidized-bed reactor.